1. Field of the Invention
The present invention relates to the field of tools for removing broken or frozen fasteners from a workpiece and, more particularly, to devices that remove rotary fasteners by applying a torque in a direction opposite to that initially necessary to drive the fastener into the workpiece.
2. Background of the Invention
To extract a broken fastener embedded in a workpiece, one often begins with a device to rotatably engage the head of the fastener. Other tools forcibly pull out or bore out the fastener.
Devices currently exist to extract head-less screws and other broken fasteners still embedded in a workpiece. Typically these devices include drilling tools that bore into the fastener. See U.S. Pat. No. 6,081,983 awarded to Hogson, et al. (2000), U.S. Pat. No. 5,546,834 awarded to Gable et al (1996), U.S. Pat. No. 5,544,987 awarded to Gipson (1996) U.S. Pat. No. 5,279,187 awarded to Salmon (1994).
As the tool bores into the fastener, it is hoped that the largest portion of the applied torque imparts a fastener-extracting force to the fastener. However, in actuality a large portion of the torque results in the tool being forced further into the fastener and the workpiece. This further penetration into the workpiece does not necessarily facilitate eventual extraction of the fastener but instead may result in damage to the workpiece.
There are devices that comprise a left handed cutting tool at one end and a left handed drill bit at the other. See for instance U.S. Pat. No. 5,031,487 awarded to Polonsky on Jul. 16, 1991. These devices have several disadvantages, including: (a) the necessity for manual handling of the device when switching from use of the cutter to use of the drill bit; (b) exerting a torque along the axis of the fastener rather than exerting a torque on the fastener's periphery—the best arrangement being the simultaneous exertion of a torque along the axis and on the periphery; and (c) the difficulty of finding a point where a power tool may grip the device. Another disadvantage in the prior art is that there is insufficient control of the direction in which the device acts. Sudden changes in the resistance offered to the tool result in changes in the direction in which the tool bores into the fastener or applies an extracting torque thereto.
A need exists in the art for a device to remove broken fasteners from a workpiece that would maximize the amount of torque that is applied to the fastener and ensure rapid, smooth, and safe operation. The device should combine the application of torque along the periphery of the fastener with application of torque at the longitudinal axis of the fastener.